This is a blind systematic follow-up study by personal interview of 153 inpatients diagnosed as having schizoaffective and related psychoses (i.e. schizophreniform illness, nonprocess schizophrenia and acute schizophrenia) and their first degree family members. This group of 153 patients constitutes a sample of a total of 305 patients with the same diagnosis whose records will be studied first. The purpose of this study is to resolve the disagreements concerning the nature of this group of psychoses by testing the hypotheses that schizoaffective and related psychoses are: (a) a variant of schizophrenia, (b) a variant of affective disorder, (c) a third psychosis, defined by criteria and distinct from both schizophrenia and affective disorder, (d) a group of psychoses which at first cannot be diagnosed but eventually are recognizable as either schizophrenia or affective disorder. The proposed diagnostic criteria for a third psychosis are based on the following: (a) The psychotic patients should have a sufficient number of severe affective symptoms to make the diagnosis of schizophrenia unlikely, at least six out of a total of 17 affective symptoms. The six or more affective symptoms may meet the criteria for depression, mania, both, or neither. (b) The psychotic patient should have a sufficient number of qualitatively different severe thought and behavior disorders to make the diagnosis of affective disorder unlikely, at least two out of a total of five. The two or more qualitatively different severe thought and behavior disorders may or may not be sufficient to meet the criteria for schizophrenia when combined with other evidence of psychopathology. (c) The psychotic patient should have at least one of the following symptoms that are considered relatively common in schizoaffective and related psychoses: perplexity, confusion, bewilderment, acute onset or episodic course. (d) The psychosis must not be due to or associated with alcohol or drug abuse. After the third psychosis is established by criteria its course and outcome are to be studied.